Waveguide with Excitation Input

This example is a first step towards excitation-continuous instruments, such as wind instruments. Instead of initializing the waveguides with a single excitation function, they are fed with an input signal.

// waveguide_input.dsp
//
// waveguide with excitation by input signal
//
// - one-pole lowpass termination
//
// Henrik von Coler
// 2020-11-19

import("all.lib");

// use '(pm.)l2s' to calculate number of samples
// from length in meters:

segment(maxLength,length) = waveguide(nMax,n)
with{
nMax = maxLength : l2s;
n = length : l2s/2;
};

// one lowpass terminator
fc = hslider("lowpass",1000,10,10000,1);
rt = rTermination(basicBlock,*(-1) : si.smooth(1.0-2*(fc/ma.SR)));

// one gain terminator with control
gain = hslider("gain",0.5,0,1,0.01);
lt = lTermination(*(-1)* gain,basicBlock);

// a simple allpass (Smith Paper)
s = hslider("s",0.9,0,0.9,0.01);
c = hslider("c",0.9,0,0.9,0.01);
allpass = _ <: *(s),(*(c):(+:_)~(*(-s))):_, mem*c:+;

// another allpass
g = hslider("g",0.9, 0,0.9,0.01);
allp = allpass_comb(2,1,g);

scatter = pm.basicBlock(allpass);

idString(length,pos,excite) = endChain(wg)
with{

nUp   = length*pos;
nDown = length*(1-pos);

wg = chain(lt : segment(6,nUp) : out : in(excite) : scatter : segment(6,nDown) :  rt); // waveguide chain
};

exc = select2(gain>0.9,1,0);

length = hslider("length",1,0.1,10,0.01):si.smoo;

process(in) = idString(length,0.15, in) <: _,_;


Envelopes: Exponential

For percussive, plucked or struck instrument sounds, the envelope needs to model an exponential decay. This is very useful for string-like sounds but most importantly for most electronic musicians, it is the very core of kick drum sounds.

In contrast to the ADSR envelope, the exponential one does not contain a sustain portion for holding a sound. The only parameter is the decay rate, allowing quick adjustment. Alternative to an actual exponential, a modified reciprocal function can be used for easier implementation. The factor $d$ controls the rate of the decay, respectively the decay time:

$$e = \frac{1}{(1+(d t))}$$

The following example adds a short linear attack before the exponential decay. This minimizes clicks which otherwise occur through the rapid step from $0$ to $1$:

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Attack Time:

Decay Time:

Controlling SC with the Mouse

A quick way of control is often needed when testing and designing synthesis and processing algorithms in SuperCollider. One quick way is to map the mouse position to control rate buses. Combined with a touch display, this can even be an interesting means for expressive control. This example first creates a control bus with two channels. The node ~mouse uses the MouseX and MouseY UGens to influence the two channels of this bus:

// mouse xy controll with busses
~mouse_BUS = Bus.control(s,2);

~mouse   = {
Out.kr(~mouse_BUS.index,   MouseX.kr(0,1));
Out.kr(~mouse_BUS.index+1, MouseY.kr(0,1));
}.play;


Exercise

Exercise

Use the mouse example with the previous sawtooth-filter example to control pitch and filter characteristics.

Send and receive objects allow a wireless connection of both control and audio signals. The objects are created with send and receive or short s and r for control rate signals and get one argument - a string labeling the connection.